The onBeforeCellRender event is fired before the calendar cells are rendered. It lets you customize the cell content and appearance.
DayPilot.Calendar.onBeforeCellRender(args);
Cell properties (args.properties):
The args.properties object is available since 2021.4.5145. In prior versions, these properties are available directly in the args.cell object (e.g. args.cell.cssClass).
dp.onBeforeCellRender = function(args) { if (args.cell.start.getHours() === 13) { args.cell.properties.backColor = "silver"; } };